package com.cyc.rw;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCacheLock myCache = new MyCacheLock();
        //开启线程进行写操作
        for (int i = 1; i < 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.put(temp+"",temp+"");
            },String.valueOf(i)).start();
        }
        //开启线程进行读操作
        for (int i = 1; i < 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.get(temp+"");
            },String.valueOf(i)).start();
        }
    }
}
/**
 * 自定义缓存
 */
class MyCacheLock{
    private volatile Map<String,Object> map = new HashMap<>();
    //读写锁，更加细粒度地控制
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    //写入的时候，只希望同时只有一个线程在写
    public void put(String key,String value){
        //加写锁
        readWriteLock.writeLock().lock();
       try {
           System.out.println(Thread.currentThread().getName()+"  写入 "+key);
           map.put(key,value);
           System.out.println(Thread.currentThread().getName()+"  写入 "+key+"  OK");
       }catch (Exception e){
           e.printStackTrace();
       }finally {
           readWriteLock.writeLock().unlock();
       }
    }

    public void get(String key){
        readWriteLock.readLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"  读取 "+key);
            String o = (String) map.get(key);
            System.out.println(Thread.currentThread().getName()+"  读取 "+key+"  值为 "+o);
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            readWriteLock.readLock().unlock();
        }
    }
}

